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Optimizing Cardiac Surgery

What is Nonin Medical's EQUANOX™ Advance Technology?

Nonin Medical's EQUANOX™ Advance Technology is the patented sensor architecture that is used in Nonin Medical's EQUANOX advance 8004CA and 8004CB regional oximetry sensors.

In order to fully appreciate the advantage of this unique sensor design, one must have an understanding of the core principles of Near Infrared Spectroscopy (NIRS) Regional Oximetry and other laws.

How does NIRS Regional Oximetry Work?

Spectroscopy refers to the study of the interaction between matter and radiated energy — in this case, light. NIRS is simply the use of light in the near infrared spectrum to make measurements in matter. NIRS-based technology is used in many fields of science, from astronomy to agriculture. Common examples of the use of NIRS in medicine include pulse oximetry, capnometers, co-oximeters, hematocrit/oxygen saturation monitors, and regional (cerebral) oximeters.

Near-Infrared (NIR) light is in the spectrum ranging from 700-900 nanometers (nm). NIR light is able to pass through tissue, including bone. Currently marketed regional oximeters use between two and five wavelengths of NIR light. Figure 1 shows the absorption rates of oxygenated and deoxygenated hemoglobin across a spectrum of wavelengths and the four specific wavelengths that are used in Nonin Medical's EQUANOX advance sensors.

FIGURE 1

Scientific Principles

There is a basic principle of physics known as the Beer-Lambert Law that states one can use specific wavelengths of light and known properties of absorption of a substance (in this case hemoglobin) to measure the concentration of that substance. 

When measuring hemoglobin in tissue, such as the brain, an additional process called spacial resolution is used to distinguish between cerebral oxygen saturation and extracranial contamination from the scalp and skull. Spacial resolution refers to the use of multiple light emitters and detectors that measure different tissue depths. The depth of tissue measurement is approximately half the distance from the light emitter to the detector.

In regional oximetry, there are typically two light detectors: a near detector that measures the shallow path, and a far detector that measures both shallow and deep tissue. An algorithm is used to subtract the shallow path data from the deep path data, isolating only the deep tissue or cerebral cortex. 

EQUANOX Advance Technology

Where is regional oximetry used?

  • Adult cardiac surgery: All cases or complex cases such as deep hypothermic circulatory arrest
  • Adult ICU: Post-operative, ECMO, LVAD, IABP, resuscitation, compartment syndromes
  • Adult surgery: Vascular (carotid endarterectomy) and orthopedic shoulder procedures in the beach chair position
  • Pediatric/Neonatal cardiac surgery: Pre-, intra-, and post-operative

  • Pediatric/Neonatal ICU: Pre- and post-operative, ECMO, resuscitation, Necrotizing enterocolitis, persistent pulmonary hypertension, PDA, RDS

Dual Emitters/Dual Detectors

EQUANOX Advance Technology uses two light emitters and two detectors to effectively target the cerebral cortex and eliminate extracranial contamination from the scalp and skull (see Figure 2), proven to be the industry's least affected by intervening tissue or surface effects1.


FIGURE 2


Four Wavelengths of NIR Light

The four wavelengths of NIR light used by EQUANOX Advance Technology allows for the accurate measurement of oxygenated and deoxygenated-hemoglobin, and compensates for tissue factors that otherwise could reduce the accuracy of the measurement. The result is highly accurate measurements that correlate with the patient's true physiology2.

Sensor Design and Signal Processing Expertise

Nonin Medical is a technology company founded by engineers in 1986, and has more than 26 years of experience using NIRS. In fact, Nonin Medical invented fingertip pulse oximetry.

This extensive NIRS signal processing experience provided the foundation for a sensor design that goes even further in isolating the target tissue. Extensive electromagnetic shielding minimizes interference from other electromechanical devices. Real-time iterative algorithms assess and remove ambient light interference. These two design elements of the EQUANOX Advance Technology limit the noise and interference from external sources.

Dynamic Compensation

Nonin's Dynamic Compensation™ is a real-time smart algorithm that incorporates information from the tissue being interrogated into the measurement estimate, accounting for brain development and associated tissue changes in the first few years of life — specifically myelination of neurons and the proliferation and organization of synpases.3

As a result, the EQUANOX advance 8004CB sensor accounts for variation in light scattering associated with age, brain development and cerebral vasodilation to permit accuracy over a wide range of patient demographics and conditions3. The EQUANOX advance 8004CB sensor can be used on any patient less than 40 kilograms and does not require patient information to be entered into the monitor, such as age or size.

Conclusion

Nonin Medical's EQUANOX Advance Technology utilizes four wavelengths of NIR light, patented dual emitter/dual detector sensor architecture and thoughtful sensor design. This results in:

  • absolute accuracy
  • effective targeting of the cerebral cortex
  • proven repeatability and consistency of measurement

In addition, the EQUANOX Advance 8004CB sensor automatically takes into account the light attenuation changes caused by myelination variation, providing improved clinical utility. EQUANOX Advance Technology provides clinicians regional oximetry readings that can be acted on with confidence.

References

  1. Davie SN, et al. Impact of Extracranial Contamination on Regional Cerebral Oxygen Saturation: A Comparison of Three Cerebral Oximetry Technologies. Anesthesiology. 2012; 116(4): 834-40.
  2. MacLeod D, et al. Development and Validation of a Cerebral Oximeter Capable of Absolute Accuracy. Journal of Cardiothoracic and Vascular Anesthesia. December 2012; 26(6): 1007-1014.
  3. Kreeger R, et al. Evaluation of a Pediatric Near-Infrared Cerebral Oximeter for Cardiac Disease. The Annals of Thoracic Surgery. 2012; 94: 1527-33.

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